During a photon counting Computed Tomography (CT) process, energy levels of X-rays that have become incident are measured by counting individual incident X-rays so as to obtain a spectrum of X-rays that have passed through an examined subject. After that, in the photon counting CT process, materials contained in the examined subject are identified on the basis of the obtained spectrum so as to generate an image of the materials.
Further, it has become more and more necessary in recent years to reduce radiation exposure amounts during medical examinations. Because photon counting CT processes are not affected by circuit noise in contrast to conventional CT processes of integral types, photon counting CT processes are able to reconstruct images having high quality. For this reason, a photon counting CT process is expected to require a lower radiation dose to acquire an image having a similar level of image quality to that of an image acquired by performing a conventional integral-type CT process. As explained herein, also from the viewpoint of reducing radiation exposure amounts, there is a demand for making photon counting CT processes available in products available on market.